Safety device for airplane automatic pilots



Feb. 2, 1937. A CARLSQN 2,069,214

SAFETY DEVICE FOR AIRPLANE AUTOMATIC PILOTS Filed Nov. 2,'19s4 2 Sheets-Sheet 1 Y1 6 a v: i 7 A 3 @Eg //7" E ENTOR BERT G. hmsorv Feb. 2, 1937. CARLSQN 2,069,214

SAFETY DEVICE FOR AIRPLANE AUTOMATIC PILOTS Filed Nov. 2, 1954 2 sheets-shed 2 I INVE TOR QERT 649150 #15 ATTOIRNEY.

. 20 Fig. 4 is an end view of the unit. ton or valve 26 normally held on its double seat Patented F eb. 2, 1937 I UNITED STATES PATENT OFFICE SAFETY DEVICE FOR AIRPLANE AUTO- MATIC PILOTS Bert G. Carlson, Queens Village, N. Y1, assignor to Sperry Gyroscope Company, Inc., Brooklyn, N. Y., a corporation of New York Application November 2, 19%, Serial No, 751,143 7 Claims. (o1. 244-29 This'invention relates to servo motors for actureturning through the other piper, and vice versa ating the control surfaces of dirigible vehicles when a turn in the other direction is desired. and especially of air-planes, with especial appli- The oil from the pipe l3 enters (or leaves) cation to servo motors of automatic pilots. By through port l into annular chamber is formed 5 means of my invention the human pilot can asbetween the interior wall of the outer casing I1 5 sume instant control of the aircraft at any time, and the reduced end l8 of a sleeve l9. Oil from regardless of the position, condition or complete the other pipe l2 passes through anopening 20 breakdown of the pilot or servo motor system. to the interior of said sleeve and normally passes Referring to the drawings showing a preferred out again through the port 2| into the channel 22 form of my invention, leading through port 23 into one end of the cyl- 10 Fig. 1 is a plan view of a servo motor unit, illusinder I. Similarly, oil in the channel I5, ifuntrating diagrammatically the connection thereof der pressure, will flow through port 24 into chanto the control surfaces and to the manual opnel 22' and through port 23' into the other end erating means. of the cylinder, the two channels 22 and 22' be- Fig. 2 is a partial vertical section, on a larger ing normally separated by the closed cylinder by- 15 scale, through one of the servo motor cylinders pass valve 25. and control valves. Normally closing the interior [9' of the sleeve Fig. 3 is a transverse section taken approxil9 and'also closing one end of the channel l6 mately on line 33 of Fig. 2. around the exterior bfsaid sleeve, is a safety pis- 0 Fig. 5 1s a detail of the stop device on the byon the end of sleeve I9 and on annular face 4| pass valve. on-the interior ofhousing IT, by a spring 21. The invention is shown as applied to the form Said spring is shown as adjustable as to tension of hydraulic servo motor disposed in applicant's by means of set screw 28, against a collar 29 of copending application joint with Elmer A. Sperry, which the left hand end of said spring bears. 25 Jr. and Mortimer F. Bates, now Patent #1,992,970, Preferably the eiiective areas of the piston or dated March 5, 1935, for Hydro-pneumatic autovalve face exposed to the pressures within the matic pilot. According to this system, hydraulic chamber l9 and within the chamber 15 are made servo motor cylinders I, 2 and 3 are provided, one equal, so" that the piston will open under the same 30 for each of the three controls, i. e., rudder R, elepressure, whether it be supplied through pipe 12 3o vatorsE and ailerons A, and each cylinder is conor pipe It. When the piston opens due to extrolled from a master valve (not shown) controlcessive oil pressure, it will be seen that a bypass ling the flow of oil toone side or the other of is provided so that the oil from the high presthe several pistons 4, the master valve, in turn, sure side may flow to the low pressure side being controlled from the pneumatically operdirectly and without moving the piston 4. Pref- 35 ated differential pressure means controlled by erably small relief valves, as shown in the base the gyroscopic control unit. The several conof the piston 28, prevent any oil which leaks past trol surfaces are-shown as actuated from the the piston from building upa'back pressure. Said several pistons by means of wires running thererelief valves are shown at 3| and 32, the latter 40 from to both of the opposite ends of the sevbeing in communication with the chamber I 8' 4o eral piston rods 5, 6 and l. Preferably the same and the former with the chamber l5 and operwires lead to the several hand control levers or ating to open in case the back pressure builds up pedals by which the pilot controls the surfaces higher than the pressure on the front thereof. 'A when the automatic pilot is not working. As safety piston similar to 26 is of course provided Q5 shown, the wire from the rudder R is also confor the other cylinders 2 and 3 within housings nected to the foot pedals or other steering del1 and l1". 7 a vice 9. A wire from the ailerons also leads to As an additional safety device I also provide a the banking control handle it and a wire from means for opening at will the cylinder or bythe elevators also leads to the climb and dive pass valve 25, which hasa transverse bore 40 59 control handle I l. therethrough. Said valve is shown as mounted in Referring to Fig. 2, the pipes l2 and t3 lead to v a common stem 33 withthe corresponding bythe master control valve for'one of the cylinders, pass valves 25' and 25" for the other two cylinfor instance cylinder I, the oil (or other liquid) ders 2 and 3 (see Fig. 3) and on said stem isshown pressure being supplied through one pipe when a pulley 34, or other device for turning the same the rudder is to be turned in one direction, and byhand. Said pulley may be operated by means 55 of a wire 35 leading to a control handle 36 adjacent the aviator. A stop segment 31 is shown on the rear of said stem 33 (see Fig. which strikes against a fixed stop pin or quadrant 38 on a closure 39 for the chamber 40', within which said valves are mounted.

, The operation of my device is as follows: When under control of the automatic pilot, the several servo motors operate the several control surfaces by the displacement of the pistons 4 within the cylinders l, 2 and 3. In case a pilot desires to cut out the automatic control, he rotates the handle 36 to rotate the bypass valves on stem 33 to by pass the oil pressure.- Under these conditions the manual movement of any one of the controlhandles will move the rudders through the same wires, the pistons moving with the ruddersunopposed by oil pressure. This constitutes the normal means, for operating manually during landing and take-off. If, however, this throw-out means fails, or for any reason the pilot cannot disconnect the automatic control, he may still control the airplane by hand in any plane by exerting a greater force than normal on the proper control foot pedals 9, or handles 10 and II. This unusual pressure will be transmitted to the oil through the piston 4 and will cause the piston 26 to open in the line affected, thus allowingthe oil to bypass and permitting the control surface to be operated. By this means the hydraulic servo motor system cannot lock the controls and prevent them from being operated by the aviator at any time.

In accordance with the provisions of the patent statutes, I have herein described the principle and, operation of my invention, together-with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combination and relations described, some of these may be altered and others omitted without interfering with the more general results outlined, and the invention extends to such use. Y

' Having described my invention, what I claim and desire to secure by Letters Patent is:

1. In a safety device for hydraulic servo motors for aircraft having an operating cylinder and piston, a rudder operated thereby and alternative hand means for operating said rudder, means for supplying liquid under pressure to either side of said piston, a safety piston at said operating cylinder having a pressure face exposed to said liquid pressure regardless ofwhich sde of the main piston the pressure'is applied to, a loading spring for said safety piston, and a safety bypass for the liquid from the high to the return side opened by movement of said safety piston against said spring, said safety bypass being independent of the operation of said liquid supplying means.

2. In a safety device for hydraulic servo motors for aircraft and the like, separate passages for leading the liquid to and from the motor in either direction, a bypass valve therebetween, comprising 'a sleeve, the interior of which is exposed to -the liquid pressure in one passage and the exterior to the liquid pressure-in the other passage, a valve face normally seating on the end of said sleeve, the area thereof exposedto the-liquid withspring means for yieldingly holding said valve closed except when subject to more than normal pressure. v p

3. In a safety device for hydraulic servo motors for aircraft having an operating cylinder and piston, a rudder operated thereby and alternative hand means for operating said rudder, means for supplying liquid under pressure to move the piston in either direction, said operating cylinder having a bypass passage associated therewith between the high and the return side of the liquid supply, a loaded safety valve operating independently of said liquid supply means for closing said bypass passage and having its face simultaneously subjected-to pressures existing on both sides of the operating cylinder piston and adapted to open when the pressure of the liquid on either side of the cylinder piston exceeds-the normal working pressure, whereby the pilot may turn the rudder by over-controlling'the servo motor.

4. In a safety device for hydraulic servo motors for aircraft and the like, separate passages for leading the liquid to and from the motor in either direction, a bypass valve therebetween, comprising a sleeve, the interior of which is exposed to the liquid pressure in one passage and the exterior to the liquid pressure in the other passage, a valve face normally seating on the end of said sleeve, the area thereof exposed to the liquid within and without said sleeve being the same, relief valves in said face for preventing the building up of back pressure, and spring means for yieldingly holding said valve closed except when subject to more than normal pressure. a

5. In a semi-automatic control system for aircraft, a hydraulic servo motorfor each control rudder, alternative manual control means for each rudder, means whereby pressure fluid is supplied to move each motor in either direction, and a pressure responsive safety valve for each motor having its pressure face subjected at all times to the pressures existing on both sides of its respective servo-motor piston to permit any rudder to be manually operated by overcontrolling its motor, regardless of the operation of said fluid supply means. g

6. In a safety device for hydraulic" servo motors for aircraft having an operating cylinder and piston, a rudder operated thereby and'alternative hand means for operating said rudder, a pair of passages for supplying liquid under pressure and returning the same to move the piston in either direction, said operating cylinder having a bypass passage between the two ends of the cylinder, and a loaded safety valve for normally closing said bypass passage, having an operating surface exposed to the oil pressure in each end of said cylinder and adapted to bypass the liquid from one side of the piston to theother when the pressure of the liquid within either end of the cylinder exceeds the normal working pressure, whereby the servo motor.

"l. A safety bypass for hydraulic servo motors for aircraft, as claimed in claim ,6, wherein the valve device is formed by a spring load d single valve normally closing twoopeningsof/equal area which are connected to bypass the l quid between the two ends of the'cylin'der wh opened.

the valve is -BERT:G. chin-son. 

